Uganda lies within the drier end of the natural distribution range of Coffea canephora and contains unexplored genetic material that could be drought-adapted and useful for developing climate-resilient varieties. Using experimental treatments, (i) ample and (ii) restricted-water, response of 148 genotypes were studied comprising wild, feral and cultivated C. canephora. Biomass allocation, standing leaf area and leaf area growth data were collected. Linear mixed effect models and PCA were used to analyse effect of drought on genotypes from different: (i) cultivation status, (ii) genetic groups and (iii) locations. We assessed the relationship between drought tolerance for relative growth rate in leaf area (RGRA), total number of leaves (TNL), total leaf area (TL) and total leaf dry weight (TLDW) of genotypes at final harvest. Restricted-water reduced RGRA across genetic groups (3.2 – 32.5%) and locations (7.1 – 36.7%) but not cultivation status. For TNL, TL and TLDW, genotypes that performed well in ample-water performed worse under restricted-water, indicating growth-tolerance trade-off. Drought tolerance in RGRA and TNL were negatively correlated with wetness index suggesting some degree of adaptation to local climate. Findings indicate a growth-tolerance trade-off within this tropical tree species and drought tolerance of Uganda’s C. canephora is somewhat associated with local climate.

Recent research has shown that plants can distinguish genetically-related individuals from strangers (kin recognition) and exhibit more cooperative behaviours towards these more related individuals (kin discrimination). The first evidence for this was found when Cakile edentula plants growing with half-sibs allocated relatively less biomass to roots than plants growing with unrelated individuals, indicating that kin recognition can reduce the intensity of competition (Dudley & File, 2007). Since then, kin discrimination has been shown to result in reduced competition for soil resources (Semchenko, Saar, & Lepik, 2014), light (Crepy & Casal, 2015) and pollinators (Torices, Gómez, & Pannell, 2018). On the other hand, allelopathy, plants producing chemical compounds that negatively affect performance of neighbour plants, has also been widely documented (Inderjit & Duke, 2003) and shown to profoundly affect local species coexistence and plant community structure (Meiners, Kong, Ladwig, Pisula, & Lang, 2012). In crops allelopathy can also be beneficial in suppressing weeds (Macías, Mejías, & Molinillo, 2019). In the current issue, Xu, Cheng, Kong, and Meiners (2021) published the first study to show that kin discrimination can also affect the balance between direct competition for resources and allelopathy, and this together may lead to improved weed suppression in rice.

Lianas are a distinctive component of tropical forests and their increase in abundance may have profound ramifications for forest composition and ecosystem functioning. However, so far, the current view considers lianas as a single, functional plant type and, therefore, ignores the life history differences among species resulting from their climbing mechanisms. Here, we integrate data from the main functional traits used to characterize plant form and function with global abundance data to reveal that lianas consistently have differences associated with their main climbing mechanisms. Overall, lianas with active climbing were characterized by an acquisitive strategy, showing higher specific leaf area, foliar nitrogen and slightly higher (marginally significant) maximum photosynthetic rates compared to lianas with passive climbing. Using structural equation modeling, we show that across the tropics the abundance of lianas with active climbing is mainly determined by forest structure (stem size distribution). Our study shows that active and passive climbing lianas clearly diverge in their functional traits and factors affecting their distribution. We conclude that a shift in the current view, where lianas are considered a single, functional plant type, is urgently needed to increase our predictability of their effects on tropical forests in the future.

The phenomenon that organisms can distinguish genetically related individuals from strangers (i.e. kin recognition) and exhibit more cooperative behaviors towards their relatives has been documented in a wide variety of organisms. But its occurrence in plants has only been recently considered. What emerges is that, while concerns remain about some methodologies used to document kin recognition, there is sufficient evidence to state that it exists in plants. Effects of kin recognition go well beyond reducing resource competition between related plants, and involve interactions with pollinators, pests and diseases as well as symbionts (mycorrhizal networks). It thus likely has important implications for diversity of plant populations, ecological networks and community structure. Such effects need to be further explored. Moreover, as kin selection may result in less competitive traits and thus greater population performance, it also holds promise for crop breeding. However, one would need to consider that (i) growing crops of strongly related plants will evidently forego advantages of crop diversification and (ii) outcomes of kin recognition tend to depend on environmental conditions. Therefore, the primary questions that need to be answered are: when, where and by how much kin recognition improves population performance.